公开(公告)号：CA2551988C

公开(公告)日：2010-03-16

申请号：CA2551988

申请日：2005-01-07

Applicant: QUALCOMM INC

Inventor： VIJAYAN RAJIV ,  GUPTA ALOK KUMAR ,  KRISHNAMOORTHI RAGHURAMAN

IPC: H04L27/26

Abstract: Frequency error estimation and frame synchronization are performed at a receiver in an OFDM system based on a metric that is indicative of detected pilot power. The metric may be defined based on cross-correlation between two received symbols obtained in two OFDM symbol periods. For frequency error estimation, a metric value is computed for each of multiple hypothesized frequency errors. The hypothesized frequency error for the metric value with the largest magnitude is provided as the estimated frequency error. For frame synchronization, a correlation value is obtained for each OFDM symbol period by correlating metric values obtained for NC (e.g., most recent) OFDM symbol periods with NC expected values. The expected values are computed in a manner consistent with the manner in which the metric values are computed. Peak detection is performed on the correlation values obtained for different OFDM symbol periods to determine frame synchronization.

公开(公告)号：RU2335853C2

公开(公告)日：2008-10-10

申请号：RU2006130748

申请日：2005-01-28

Applicant: QUALCOMM INC

Inventor： GUPTA ALOK KUMAR

IPC: H04L5/06 ,  H04L27/26 ,  H04L27/06

公开(公告)号：NZ548310A

公开(公告)日：2008-06-30

申请号：NZ54831005

申请日：2005-01-07

Applicant: QUALCOMM INC

Inventor： VIJAYAN RAJIV ,  GUPTA ALOK KUMAR ,  KRISHNAMOORTHI RAGHURAMAN

IPC: H04L27/26

Abstract: Frequency error estimation and frame synchronization are performed at a receiver in an OFDM system based on a metric that is indicative of detected pilot power. The metric may be defined based on cross-correlation between two received symbols obtained in two OFDM symbol periods. For frequency error estimation, a metric value is computed for each of multiple hypothesized frequency errors. The hypothesized frequency error for the metric value with the largest magnitude is provided as the estimated frequency error. For frame synchronization, a correlation value is obtained for each OFDM symbol period by correlating metric values obtained for NC (e.g., most recent) OFDM symbol periods with NC expected values. The expected values are computed in a manner consistent with the manner in which the metric values are computed. Peak detection is performed on the correlation values obtained for different OFDM symbol periods to determine frame synchronization.

公开(公告)号：CA2600463A1

公开(公告)日：2006-09-21

申请号：CA2600463

申请日：2006-03-10

Applicant: QUALCOMM INC

Inventor： GUPTA ALOK KUMAR

IPC: H04L27/26

Abstract: Systems and methods are provided for efficiently determining frequency estimates in a forward link only wireless receiver. In one embodiment, a method is provided to compute a one shot frequency estimate. The method includes representing an arc tangent function in a table that describes elements of the function and employing the arc tangent function to compute phase information for a wireless device.

公开(公告)号：MXPA05010839A

公开(公告)日：2005-12-16

申请号：MXPA05010839

申请日：2004-04-06

Applicant: QUALCOMM INC

Inventor： GUPTA ALOK KUMAR

IPC: H04L27/26 ,  H04L00/00

Abstract: Se proporcionan las tecnicas para rastrear el error de frecuencia residual y el ruido de fase en un sistema de OFDM. En un receptor, cada simbolo de OFDM recibido se transforma con una FFT para obtener simbolos de modulacion recibidos, que se emiten en serie. Un circuito de bloqueo de fase (PLL) opera en los simbolos de modulacion recibidos emitidos en serie y proporciona un valor de correccion de fase independiente para cada simbolo de modulacion recibido. Cada simbolo de modulacion recibido se corrige con su propio valor de correccion de fase para obtener un simbolo corregido en fase. Se detecta el error de fase en cada simbolo corregido en fase para obtener un calculo de error de fase para ese simbolo corregido en fase. El calculo de error de fase para cada simbolo corregido en fase se filtra (por ejemplo, con un filtro de circuito de segundo orden) a fin de obtener un calculo de error de frecuencia, el cual se acumula para obtener un valor de correccion de fase para otro simbolo de modulacion recibido. Los simbolos corregidos en fase no se correlacionan debido a que se utilizan valores de correccion de fase independientes para los simbolos de modulacion recibidos.

公开(公告)号：AU2005208693A1

公开(公告)日：2005-08-11

申请号：AU2005208693

申请日：2005-01-28

Applicant: QUALCOMM INC

Inventor： GUPTA ALOK KUMAR

IPC: H04L27/26

Abstract: A robust initial frame detection and symbol synchronization system and methodology are provided. In particular, a first pilot is employed in conjunction with three acquisition stages. In the first stage, an attempt is made to observe the leading edge of the correlation curve associated with the first pilot symbol. In the second stage, a determination is made as to whether a leading edge was detected in the first stage by attempting to observe a flat portion and/or trailing edge of the correlation curve. Furthermore, during this second stage, a frequency loop can be updated to account for frequency offset. The third stage is for observing the trailing edge of the curve if it was not already observed in stage two. Upon detection and confirmation of receipt of the first pilot, a second pilot can subsequently be employed to acquire fine symbol timing.